It makes sense but in a post AI world - what is of value? Not the software itself, but data and network effects. MS needs to move from a world where their proprietary software makes money, to one where they enable a captive network and have data; Github provides both.
So maybe them providing service at literally all costs to themselves is a smart strategy long term.
Pretty sure compute, storage, and transit are all of value, pre and post AI. At least, pretty sure those things still cost GitHub money.